Potassium Silanide (KSiH3): A Reversible Hydrogen Storage Material

KSi silicide can absorb hydrogen to directly form the ternary KSiH3 hydride. The full structure of alpha-KSiD3, which has been solved by using neutron powder diffraction (NPD), shows an unusually short Si-D lengths of 1.47 angstrom. Through a combination of density functional theory (DFT) calculations and experimental methods, the thermodynamic and structural properties of the KSi/alpha-KSiH3 system are determined. This system is able to store 4.3 wt% of hydrogen reversibly within a good P-T window; a 0.1 MPa hydrogen equilibrium pressure can be obtained at around 414 K. The DFT calculations and the measurements of hydrogen equilibrium pressures at different temperatures give similar values for the dehydrogenation enthalpy (approximate to 23 kJmol(-1) H-2) and entropy (approximate to 54 JK(-1)mol(-1) H-2). Owing to its relatively high hydrogen storage capacity and its good thermodynamic values, this KSi/alpha-KSiH3 system is a promising candidate for reversible hydrogen storage.